1. Field of the Invention
The present invention relates to the removal of a first immiscible liquid from a liquid mixture and is especially suited to removing oil from an aqueous mixture.
2. Description of the Prior Art
Concern over pollution of the environment has dramatically increased in recent years, especially concern over pollution of water by an immiscible liquid thereon such as hydrocarbons, e.g., oil. The concern has been evidenced by the many patents recently granted which are directed to cleaning up oil spills on seas, lakes, rivers, etc., of which U.S. Pat. Nos. 3,520,806, 3,630,891, 3,518,183, 3,536,616 and 3,147,216 are representative. See also U.S. Pat. No. 3,764,527. Typical of the liquids immiscible with water are the many different types of hydrocarbons including but not limited to gasolines, kerosenes, light oils, heavy oils, jet fuel, petroleum, asphalt and paraffin crudes, diesel oil, naphtha, water immiscible ketones, aromatic solvents such as benzene, toluene and xylene, terpenes, esters, phenols, aldehydes, amides, amines, mercaptans, fatty acids, fatty acid esters, halo-hydrocarbons, polar organic compounds, and the like and these compounds will hereinafter be represented by oil, the most common polluter. The teachings of the representative patents mentioned above are primarily directed to contacting the oil to be removed, which is on the surface of the water, with a material which will absorb or adsorb oil in preference to water, and then removing the material with the absorbed or adsorbed oil from the surface of the water. The oil in some cases may later be separated from the material, if desired.
However, pollution of water by an immiscible liquid therein such as oil may also occur by discharging aqueous mixtures containing an immiscible liquid such as oil into seas, lakes, rivers, etc. For example, there are many instances in industry in which an immiscible liquid such as oil must be removed from an aqueous mixture before discharge for environmental reasons. Moreover, there are many industrial instances in which it is desirable or necessary to remove an immiscible liquid such as oil from another immiscible liquid such as water either to recycle the oil or the water, or both, for reuse. In such industrial applications, where the mixture is usually contained in a tank or similar type vessel, it is impractical to use the techniques of the foregoing patents mainly because of time, space and economic considerations. Known techniques for the removal of the oil from mixtures in vessels, exemplified by U.S. Pat. Nos. 3,915,859, 3,487,927, 3,146,192, 3,764,527 and 2,866,827, involve passing an oil absorbtive or adsorbtive material through or along the surface of the mixture in an endless fashion while continuously separating the oil from the material by, for example, compressing or "squeegeeing" the material. Other known techniques for the removal of an immiscible liquid from a liquid mixture, include settling and/or skimming or pumping operations for removing the immiscible liquid from the surface of the mixture. One such process for the removal of oil from an aqueous mixture requires pumping the mixture into a vacuum tank, allowing the mixture to settle, draining off the water and pumping the oil into a settling tank, decanting the water and finally heating the settled oil to drive off the remaining water.
These known industrial separation processes and apparatus have many disadvantages and drawbacks. For example, almost all of the foregoing industrial processes and apparatus remove considerable water and coarse solid particles along with the oil in the initial separation phase. This, of course, requires additional steps in the respective processes where further separation is desired or required. Where settling is used, appropriate vessels must be provided resulting in consumption of space and capital. All of the known processes and apparatus require the consumption of power in the pumping or heating operations or to effect movement within or by the apparatus. Known apparatus comprise many moving parts and where they include floats or skimmers are also quite bulky and are easily damaged. Moreover, the known processes and apparatus cannot easily accommodate oil level and mixture level changes and, except for settling processes, are not capable of removing heavier than water oils. In addition, since the processes involve a multitude of steps and the apparatus comprise many moving parts, personnel are continually occupied in carrying out the respective processes.
The present invention obviates these drawbacks and disadvantages and provides additional advantages, such as reduced labor, time, space, and apparatus complexity, which result in reduced costs, as well as providing significantly improved results in removing an immiscible liquid from a liquid mixture.